Fluorescence imaging is a commonly used technique for detecting components of a biological sample, such as a blood, urine, or saliva sample from a human or animal subject, to characterize an aspect of the sample. Sample components of interest are labeled with fluorescent tags that emit fluorescence upon excitation with light of an appropriate wavelength. Fluorescence imaging is used to determine the results of biological assays in a variety of applications including medical diagnostics, food safety, and forensic science. In some cases, it is necessary to perform several different assays on a single sample in a short period of time, wherein some of the different assays are mutually incompatible and therefore require separate processing. In other cases, many samples must be processed in a short period of time.
Deoxyribonucleic acid (DNA) sequencing is a prominent example of an application that benefits from parallel processing of many samples to sequence the DNA in a timely manner. Some of the more popular, commercially available DNA sequencing systems sequentially determine the order of nucleotide bases in a strand of DNA. Each base is determined through a biological assay followed by fluorescence imaging to determine the base type, i.e., adenine (A), guanine (G), cytosine (C), or thymine (T). The process to determine each base is time consuming and the overall sequencing process may have an occasional assay error leading to faulty sequencing. Therefore, the DNA strand is usually cut into a large number of shorter fragments that are processed in parallel.
DNA sequencing and many other DNA or ribonucleic acid (RNA) assays suffer from the amount of DNA or RNA material under investigation available being too low to produce a measurable result. In such situations, the DNA/RNA material may be amplified through polymerase chain reaction (PCR). PCR is a thermally mediated assay that produces many copies of a DNA or RNA molecule. The vast majority of PCR methods use thermal cycling of a sample, wherein each cycle duplicates the DNA or RNA material, eventually resulting in significant amplification of the original material. Isothermal amplification is an alternative to PCR, wherein the amplification takes place in an environment at a constant, elevated temperature.